function byte_convert($bytes)
  {
    $symbol = array('B', 'KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB');
 
    $exp = 0;
    $converted_value = 0;
    if( $bytes > 0 )
    {
      $exp = floor( log($bytes)/log(1024) );
      $converted_value = ( $bytes/pow(1024,floor($exp)) );
    }
 
    return sprintf( '%.2f '.$symbol[$exp], $converted_value );
        //we can't use PHP integer unsigned as some systems use 32 bit and other 64 bit ,so here we use C style function sprintf
  }